Answer:
[tex]86\ fifth\ graders[/tex]
Step-by-step explanation:
Let
x-----> number of students in third grade
y----> number of students in fourth grade
z---> number of students in fifth grade
r----> number of students in sixth grade
we know that
[tex]x+y+z+r=1,677[/tex] -----> equation A
[tex]z=2r[/tex] ----> [tex]r=0.5z[/tex] -----> equation B
[tex]y=3z[/tex] -----> equation C
[tex]x=5y[/tex] ----> equation D
Substitute equation C in equation D
[tex]x=5(3z)=15z[/tex] -----> equation E
Substitute equation B, equation C, equation E in equation A and solve for z
[tex](15z)+(3z)+z+(0.5z)=1,677[/tex]
[tex]19.5z=1,677[/tex]
[tex]z=1,677/19.5=86\ fifth\ graders[/tex]